Strategies for protein identiﬁcation
The techniques described in Chapter 2 allow protein mixtures to be separated into their components but do not allow those components to be identiﬁed. Indeed, the individual fractions produced by such methods are almost always anonymous. Each spot on a 2Dgel and each fraction emerging from an HPLC column looks very much like any other. In the case of 2DGE, even differences in spot size and distribution provide only vague clues about protein identity, i.e. apparent molecular mass and pI. The next stage in proteomic analysis is therefore to characterize the fractions and thus determine which proteins are actually present.